Fluoropolymer resins, and especially perfluoropolymer resins, are known for their low surface energy and antistick properties, and thermal and chemical resistance. These fluoropolymer compositions do not stick to other materials, especially dissimilar materials, with any practical degree of bond strength.
Some high temperature resistant thermoplastics, such as polyamide imide, polyarylene sulfide and polyether sulfone, have found use as polymer binders in fluoropolymer coating formulations. See, for example U.S. Pat. No. 5,230,961 (Tannenbaum) and U.S. Pat. No. 5,093,403 (Rau et al.). However, for dry powder coating such as discussed in the '403 patent, particle dimensions of the formulation components are determined by grinding or milling capabilities and limit the homogeneity of coatings fabricated from the blend. Such blends also exhibit segregation in shipping, processing and recovery of scrap powder. When using a powder mixture for electrostatic spraying, the components of the mixture tend to segregate. The segregation can produce a variable powder coating composition when the powder is sprayed on a substrate. Another notable problem occurs in electrostatic spray coating in conjunction with the sprayed powder that does not adhere to the target substrate, known as "overspray". Segregation in the overspray prevents direct recycle to the spraying operation.
There remains a need for compositions of melt-fabricable fluoropolymer with high temperature resistant polymer binder in which the components provide a more homogeneous blend, and one resistant to segregation during shipping or processing.